Bi-prediction for video coding

A method for video decoding comprising:

• determining that a video block is bi-predicted with first and second reference pictures;
• determining that the video block does not use weighted prediction (WP) for both first and second reference pictures;
• decoding a weight index of bi-prediction with coding unit weights (BCW) responsive to the video block not using the weighted prediction (WP) for both first and second reference pictures;
• determining a first BCW weight based on the weight index;
• applying the first BCW weight to a first prediction sample of the video block obtained from the first reference picture to obtain a first BCW weighted prediction sample;
• and
• decoding the video block based on the first BCW weighted prediction sample.

A device for video encoding comprising a processor configured to implement:

• determining that a video block is bi-predicted with first and second reference pictures;
• determining that the video block does not use weighted prediction (WP) for both first and second reference pictures;
• encoding a weight index of bi-prediction with coding unit weights (BCW) responsive to the video block not using the weighted prediction (WP) for both first and second reference pictures;
• determining a first BCW weight based on the weight index;
• applying the first BCW weight to a first prediction sample of the video block obtained from the first reference picture to obtain a first BCW weighted prediction sample;
• and
• encoding the video block based on the first BCW weighted prediction sample.

A method for video encoding comprising:

• determining that a video block is bi-predicted with first and second reference pictures;
• determining that the video block does not use weighted prediction (WP) for both first and second reference pictures;
• encoding a weight index of bi-prediction with coding unit weights (BCW) responsive to the video block not using the weighted prediction (WP) for both first and second reference pictures;
• determining a first BCW weight based on the weight index;
• applying the first BCW weight to a first prediction sample of the video block obtained from the first reference picture to obtain a first BCW weighted prediction sample;
• and
• encoding the video block based on the first BCW weighted prediction sample.